Molecular characterization of a Phi-class mustard (Brassica juncea) glutathione S-transferase gene in Arabidopsis thaliana by 5′-deletion analysis of its promoter

Glutathione S-transferases (GSTs) are regulated by various stimuli at the transcriptional level. In this study, a 2,640-bp promoter sequence of a mustard GST gene, BjGSTF2, was cloned. Several truncated BjGSTF2 promoters were generated by 5'-deletion, fused to the beta-glucuronidase (GUS) coding sequence and the chimeric genes expressed in Arabidopsis thaliana. Transgene expression in GST2623::GUS plants carrying the longest promoter varied considerably. GUS activity was high in the roots, cotyledons, anthers and both ends of the silique, but it was low or barely detectable in the leaves, seeds, petals and stamens. Analysis of transgenic plants expressing the GUS gene under the control of different truncated BjGSTF2 promoters revealed several regions that possessed cis-acting elements required for the basal and induced expression by H2O2, salicylic acid and 1-aminocyclopropane-1-carboxylate and down-regulation by spermidine. The results also showed that the GUS activity of GST2623::GUS coincided well with the H2O2 accumulation pattern in cultured leaf-disc explants during the regeneration process.